Al(OH)3掺杂非晶态氢氧化镍的制备及其电化学性能

采用微乳液法合成了Al(OH)3掺杂非晶态Ni(OH)2粉体.研究了温度、pH值和掺杂剂的含量等各种因素对其电化学性能的影响并分析了其作用机理.实验表明样品制备的工艺条件为t=50℃、pH=12、 Al(OH)3掺杂含量为5%时,样品电极容易活化,循环性能较好.采用以100 mA/g恒电流充电4 h,以50 mA/g恒电流放电,终止电压为1.0 V的充放电制度,其比容量达346.1 mA·h/g,放电工作电位平稳于1.24 V.     

球磨对LiVPO4F的合成及性能的影响

通过碳热还原法合成了正极材料LiVPO4F,利用XRD、SEM和充放电测试研究了球磨对LiVPO4F的合成和电化学性能的影响,结果表明:没有球磨的样品不能合成单相的LiVPO4F;球磨1 h和2 h合成的LiVPO4F样品的首次放电比容量分别为117 mAh/g和130 mAh/g,库仑效率分别为84.8%和87.2%,50次循环后,容量衰减率分别为16.2%和14.6%。     

Co、Sr复合掺杂β-Ni(OH)2纳米粒子的制备及性能

用微乳液法制备了Co、Sr复合掺杂β-Ni(OH)2纳米粒子,详细研究了合成工艺条件对化学粒子结构形态与电化学性能的影响,探讨了掺杂纳米氢氧化镍电化学活性的作用机理.对样品分别进行了XRD、TEM分析,以及充放电性能和循环伏安特性的测试.结果表明,在pH=10.5、t=40℃,掺杂剂CoSO4、SrCl2的质量分数为3%、7%时,样品的平均粒径为35 nm左右,且分布较为均匀,无明显团聚现象.该条件下制备的样品以0.1C的倍率放电,在终止电位为1.0 V时,其比容量可达286.2 mAh/g,放电工作电位平稳于1.27 V.     

改变型混合教学模式下学习评价体系构建研究

改变型混合式教学模式是现阶段促进学习质量提升的最佳方式之一,合适的学习评价体系是有效实施该教学模式的核心要素之一。第四代教育评价理论、多元智能理论、建构主义学习理论为改变型混合学习评价体系的构建提供了理论依据,评价主体多元化、方式多样化、内容全面化、工具便捷化的评价原则再结合改变型混合式教学模式的基本流程,初步构建了改变型混合学习评价体系,该体系由评价类型、节点、指标、主体、方式、权重等要素构成。     

Synthesis and electrochemical properties of Cr-doped Li<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> cathode materials for lithium-ion batteries

Cr-doped Li₃V₂(PO₄)₃ cathode materials Li₃V_2−x Cr _x (PO₄)₃ were prepared by a carbothermal reduction(CTR) process. The properties of the Cr-doped Li₃V₂(PO₄)₃ were investigated by X-ray diffraction (XRD), scanning electron microscopic (SEM), and electrochemical measurements. Results show that the Cr-doped Li₃V₂(PO₄)₃ has the same monoclinic structure as the undoped Li₃V₂(PO₄)₃, and the particle size of Cr-doped Li₃V₂(PO₄)₃ is smaller than that of the undoped Li₃V₂(PO₄)₃ and the smallest particle size is only about 1 μm. The Cr-doped Li₃V₂(PO₄)₃ samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram (CV), and electrochemical impedance spectra(EIS). The optimal doping content of Cr was that x=0.04 in the Li₃V_2−x Cr _x (PO₄)₃ samples to achieve high discharge capacity and good cyclic stability. The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through the Cr-doping. The improved electrochemical performances of the Cr-doped Li₃V₂(PO₄)₃ cathode materials are attributed to the addition of Cr³⁺ ion by stabilizing the monoclinic structure. Funded by the Guangxi Natural Science Foundation(No. 0832259) and the National Basic Research Program of China (No. 2007CB613607)     

前驱体掺杂-常温球磨还原法制备锂离子电池正极材料LiFe_(1-3y/2)Al_yPO_4

采用共沉淀法制备掺Al3+前驱体FePO4·2H2O,并以乙二酸为还原剂,与Li2CO3反应在常温下球磨合成LiFePO4前驱混合物,后经热处理得到橄榄石型LiFe1-3y/2AlyPO4。用XRD、SEM、HRTEM和恒流充放电等对样品进行表征。结果表明:适量Al3+掺杂不会破坏LiFePO4的晶体结构,当掺杂量较低时(y=0.01),Al3+优先占据Fe位;当掺杂量较高时(y≥0.02),Al3+同时占据Li位和Fe位。电化学测试表明:LiFe0.985Al0.01PO4拥有最优的电化学性能,该样品在0.1C、1C和2C倍率下的首次放电比容量分别为162.4、152.2和142.0 mA·h/g,在1C倍率下循环100次后的放电比容量高达149.7 mA·h/g。     

Synthesis and electrochemical properties of Ce-doped LiNi_（1/3）Mn_（1/3）Co_（1/3）O_2 cathode material for Li-ion batteries

The layered material of Ce-doped LiNi1/3Mn1/3Co1/3O2 with α-NaFeO2 was synthesized by a co-precipitation method. X-ray diffraction (XRD) showed that Ce-doped LiNi1/3Mn1/3Co1/3O2 had the same layered structure as the undoped LiNi1/3Mn1/3Co1/3O2. The scanning electron microscopy (SEM) images exhibited that the particle size of Ce-doped LiNi1/3Mn1/3Co1/3O2 was smaller than that of the undoped LiNi1/3Mn1/3Co1/3O2. The Ce-doped LiNi1/3Mn1/3Co1/3O2 samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram (CV), and electrochemical impedance spectra (EIS). The optimal doping content of Ce was x=0.02 in the LiNi1/3-xMn1/3Co1/3CexO2 samples to achieve high discharge capacity and good cyclic stability. The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through Ce-doping. The improved electrochemical performances of the Ce-doped LiNi1/3Mn1/3Co1/3O2 cathode materials were attributed to the addition of Ce4+ ion by stabilizing the layer structure.     

机械活化-盐酸常压浸出钛铁矿的影响

采用机械活化-盐酸常压浸出法对钛铁矿进行了选择性浸出,研究机械活化对钛铁矿的结构、形貌、粒度及浸出效果的影响。结果表明,机械活化可以细化钛铁矿的粒径,增加颗粒表面的粗糙度,从而增大其比表面积;机械活化可以破坏钛铁矿晶粒的完整性,并产生大量晶格缺陷,使晶格膨胀,上述作用均能强化钛铁矿浸出。最优浸出条件为:盐酸质量分数20%,反应温度100℃,酸矿比1.2,钛铁矿活化时间2 h。最优条件下Ti和Fe的浸出率分别为1.07%和95.5%,最终Ti和Si富集在渣中,其他元素进入浸出液。将上述得到的富钛渣煅烧获得了品位高于90%的人造金红石。     

聚苯胺复合电极的制备及电化学性能研究

以化学法合成导电聚苯胺，研究了氧化剂和掺杂剂以及反应温度和时间对聚苯胺的产率和电导率的影响。在确定的配方和工艺条件下，聚苯胺的合成产率为94％，电导率在5.6S/cm，将合成得到的聚苯胺掺杂导电粉体制备成高分子是合电极材料，在恒电流上进行充放电性能测试。结果表明，开路电位和放电电位较高，在以4mA/cm^2恒电流放电，终止电位为1．2V时，放电时间可持续16.5h，放电容量大。